package org.apache.lucene.search;

/**
 * Copyright 2007 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.spans.SpanQuery;
import org.apache.lucene.search.spans.Spans;

import java.io.IOException;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.List;

/**
 * Constrains search results to only match those which also match a provided
 * query. Also provides position information about where each document matches
 * at the cost of extra space compared with the QueryWrapperFilter. There is an
 * added cost to this above what is stored in a {@link QueryWrapperFilter}.
 * Namely, the position information for each matching document is stored. <p/>
 * This filter does not cache. See the
 * {@link org.apache.lucene.search.CachingSpanFilter} for a wrapper that caches.
 * 
 * 
 * @version $Id:$
 */
public class SpanQueryFilter extends SpanFilter {
	protected SpanQuery query;

	protected SpanQueryFilter() {

	}

	/**
	 * Constructs a filter which only matches documents matching
	 * <code>query</code>.
	 * 
	 * @param query
	 *            The {@link org.apache.lucene.search.spans.SpanQuery} to use as
	 *            the basis for the Filter.
	 */
	public SpanQueryFilter(SpanQuery query) {
		this.query = query;
	}

	public BitSet bits(IndexReader reader) throws IOException {
		SpanFilterResult result = bitSpans(reader);
		return result.getBits();
	}

	public SpanFilterResult bitSpans(IndexReader reader) throws IOException {

		final BitSet bits = new BitSet(reader.maxDoc());
		Spans spans = query.getSpans(reader);
		List tmp = new ArrayList(20);
		int currentDoc = -1;
		SpanFilterResult.PositionInfo currentInfo = null;
		while (spans.next()) {
			int doc = spans.doc();
			bits.set(doc);
			if (currentDoc != doc) {
				currentInfo = new SpanFilterResult.PositionInfo(doc);
				tmp.add(currentInfo);
				currentDoc = doc;
			}
			currentInfo.addPosition(spans.start(), spans.end());
		}
		return new SpanFilterResult(bits, tmp);
	}

	public SpanQuery getQuery() {
		return query;
	}

	public String toString() {
		return "QueryWrapperFilter(" + query + ")";
	}

	public boolean equals(Object o) {
		return o instanceof SpanQueryFilter
				&& this.query.equals(((SpanQueryFilter) o).query);
	}

	public int hashCode() {
		return query.hashCode() ^ 0x923F64B9;
	}
}
